Laser absorption spectroscopy diagnostics of helium metastable atoms generated in dielectric barrier discharge cryoplasmas

• Published in: Japanese Journal of Applied Physics Vol. 54; no. 10; pp. 106101 - 106108
• Main Authors: Urabe, Keiichiro, Muneoka, Hitoshi, Stauss, Sven, Sakai, Osamu, Terashima, Kazuo
• Format: Journal Article
• Language: English
• Published: The Japan Society of Applied Physics 01-10-2015
• Subjects: Absorption spectroscopy; Dielectric barrier discharge; Gas density; Gas temperature; Helium; Lasers; Plasmas; Quenching
• ISSN: 0021-4922; 1347-4065
• DOI: 10.7567/JJAP.54.106101

Cryoplasmas, which are plasmas whose gas temperatures are below room temperature (RT), have shown dynamic changes in their physical and chemical characteristics when the gas temperature in the plasmas (Tgp) was decreased from RT. In this study, we measured the temporal behavior of helium metastable (Hem) atoms generated in a parallel-plate dielectric barrier discharge at ambient gas temperatures (Tga) of 300, 100, and 14 K and with a gas density similar to atmospheric conditions by laser absorption spectroscopy. The increments of Tgp to Tga were less than 20 K. We found from the results that the Hem lifetime and maximum density become longer and larger over one order of magnitude for lower Tga. The reasons for the long Hem lifetime at low Tga are decreases in the rate coefficients of three-body Hem quenching reactions and in the amounts of molecular impurities with boiling points higher than that of He.